This invention relates to a press for removing liquid from aqueous pulp. In particular it relates to such a press which operates continuously with high efficiency removal of liquid at low or high pulp flow rates and at low or high levels of pulp consistency.
The need for removing liquid from aqueous pulp solution occurs often in the paper making, food processing and other similar industries. To facilitate this process mechanical presses have been devised which remove liquid by reducing the volume of the pulp. While a simple squeeze type press is efficient in removing liquid, many processes require a continuously operating press which will receive an uninterrupted supply of pulp from other machinery. Heretofore, the most successful continuously operating presses have utilized rollers or cones operating against a perforated plate for squeezing the pulp.
When these prior art presses are operated at low pulp flow rates or with pulp having a low solid consistency they are inefficient. Further, when they are operated at high pulp flow rates or with pulp having a high solid consistency, overloading often occurs stopping the pressing operation and possibly damaging the press. Overloading particularly occurs when a nonhomogeneous pulp containing varying particle size and solid consistency is processed. As a result, the prior art presses must be operated within a narrow range of pulp flow rates and consistencies unless they are shut down upon each change in pulp conditions for readjustment of their rollers. This presents a severe handicap when the presses are used in conjunction with other continuously operating equipment which discharge pulp at varying flow rates and consistencies.
An additional disadvantage of the cone or roller type presses is that they are difficult to seal. Thus a portion of the removed liquid passes back into the squeezed pulp, rewetting it.
While prior attempts have been made to improve the cone or roller presses, they have increased the complexity and cost of the presses without overcoming the basic problems.